Microwave antenna



Nov. 19, 1957 M. L. WATSON 2,814,039

MICROWAVE ANTENNA Filed May :5, 1946 2 Sheets-Sheet i L? I: i W k a l g 212 FIG. I 13 FIG. 2

I I L ll'u- INVENTOR' MICHAEL L. WATSON BY W ATTORNEY Nov. 19, 1957 M. L. WATSON MICROWAVE ANTENNA 2 Sheets-Sheet 2 Filed May 3, 1946 FIG. 3

FIG. 4

INVENTOR M ICHAEL. L. WAT SON ATTORNEY This invention relates in general to antennas, and in particular to waveguide-type radiators" for use iirli'near arrays.

This invention is applicable for use in" linear antenna arrays where" compact; light wei'giit' equipment is de sired and this inventiorr provides easil'y" adjustable coupling andsimplicity offconstructi'on of theelments:

The primary object "of this inventionis taprovidewaveguide-typeradiating elements for radiating electromag= netic energy which maybe reversed-ingpolari'tyand which' maybe fed from" a waveguide or coaxial lineto form a linear array;

Another object" of this invention is" to" provide" novel construction for lineararraysoftlie' type described.

Other and further objects'of this-inventionwillbe. apparent from the following'specifications when talenwitli the accompanying drawings in; which:

Fig. 1, is aperspective view of onetype of radiator of, this" invention;

Fig: 2is a perspective View; of another.- type ofradiator of thisinvention;

Fig; 3'isa' perspective .view'of'one form oflinear. array embodying thisinvention; and

Fig: 4 is a perspective View of another. form ofl'in'ear array embodying this invention.

in Fig. 1, isshown one type ofsinglle radiator-for use 40 in the linear array shown in Fig. 3. The radiator consistsof waveguide 10" which is one-quarter wavelength inl'ength and is short circuited at. one endias shown. This:radiator is fedbypro'be 1'1 extending cent'rall'y along. the length of the radiator andlpassing through aperture 12 in the wall. of feed waveguide 1 3": At the open end of radiator in; probe 11 is bentat right angles. and'attached to the center of one wide wall' of' radiator 1'0; thus placing the bent-section. of the, prebeparallel-to the electric fieldl As is well known the phase of "the electric field is determined by which w-all probe-H is'attached to.

lnFig: 4 there is shown the samerarrangement usingi.

a section. of circular waveguide 14 asttheyradiatorh All? other elements of this structurearewthessame as explainedi above: and are designated by the, sammnnmbers est-the: correspondingparts of the previous figure:..

The linear array of Fig. 3 uses ,thereetangular radiators as previously described in connection with Fig. 1. One construction of this array utilizes a feed-guide 15 having one wide wall thicker than one-quarter wavelength. A channel is cut out of this wide wall with width a and depth b as shown, where width a is the internal dimension of the width of feed guide 15 and depth b is onequarter wavelength. The dimension awill lie between one-halt" wavelength and one wavelength. At regular 35 intervals partitions 16 are placed in the channel with distance 0 between adjacent surfaces equal to the narrow internal dimension of feed-guide 15. The dimension c will generally be somewhat less than one-half wavelength at the operating frequency. Each partition has a thickness which permits the desired radiator spacing s between centers of each radiator thus formed. In one typical States Patent" 0 "ice are drilled in the centerof eachradiator and through thefeed-guide. U-shaped probes 1 7 are supported in a groove cut in every other'partition' l6 and the ends ofthe probes project through the feed apertures" into the main feed-guide 1'5. Theu-shaped probes provide phase reversal at every other radiator tocompensate for the increased distance-from the feed end of guide lsi This phase reversal may bebett'er understood by considering the U-shaped probe 17 as made upof" two L-shaped probes as shown in Fig. l; The fact that one of the L-sliaped probes is bent in the dii'ection'ofpropagation of energy in feed guide 15'--whilethe other L-shaped' probe is bent in a direction opposite the direction of" propagation-in' feed-guide 15* will'result in the: phase reversal mentioned above. If the distance; s is one-half' a Wavelength as suggested above,- the ends of the probes extending into feed guide' E5 will be excited'in phase opposition. The phase reversal of the U shapcd probes will compensate for the phase reversal withinfeed-guide 15' causing the rectangular radiators; to be excited in phase. If it is desired to feed all of the rectangular radiators in phase opposition this may be accomplished by using individual tt-shaped probes each bentin the same direction but" spaced one-half wavelength apart along teed-guide 15. The rectangular radiators may be at: rayed in many other and different combinations; inac cordance with well-known antenna theory;

The linear array shown in" Fig. 4 is constructed from the samefeed-guide 1'5 213 is used for the construction of'the array shown in Fig. 3. lnsteadofcutting a channel, however, cylindrical openings I8 are" drilled in the thick wide wall of guide 15. having'a. diameter e, and a depth 11, the depth beingequalto one-quarter wavelength. The dimension e should be of sufli'cient size to support the dominant mode in a circular waveguide. The spacing s will depend on the manner in which the individual antennas-are arrayed and on1the shape of the fieldpattern to be achieved. Small feed apertures 19' are drilled completely through the wall inthe center of openings 18' and U-shaped probes 20. are positioned as explained above.

The linear arrays of radiators described. produce a narrow fan-shaped beam of electromagnetic energy. This beam may be scanned either mechanically or. electrically using various well known scanning methods. This scanning may be accomplished by mechanically or electrically varying the wavelength in feed-guide 15 or by mechanically varying the position of the. array in space.

This invention is not to be limited by the. above described specifications but. is to be limited only by. the following claims.

What is claimed is:

1. Apparatus for radiating electromagnetic energy comprising a. section of waveguide one-quarter wavelength Ion-g and short circuited at one end thereof, said section of waveguide having a small aperture positioned in the center of said short circuited end through which said section of waveguide is energized; and a feed probe extending centrally along the length of said section of Waveguide, said feed probe having one end bent and fastened to a wall at the open end of said section of waveguide, said feed probe having its other end projecting through said aperture in said short circuited end of said section of waveguide whereby said feed probe when energized excites an electromagnetic field in said section of Waveguide.

2. A linear array antenna having a plurality of elements as in claim 1, which antenna comprises a length of waveguide having one thick wide wall with a channel cut therein, said wide wall having a thickness greater than one-quarter wavelength and said channel having a depth of one-quarter wavelength; a plurality of partitions at equally spaced intervals in said channel, the distance between adjacent surfaces of said partitions being equal to the narrow internal dimension of said waveguide and each of said partitions having a thickness to position the radiators thus formed a predetermined distance apart; an aperture in the center of each of said formed radiators; a groove in the upper center of alternate partitions; and a U-shaped probe, positioned in each of said grooves so that the ends of said probes project through said apertures.

3. A linear array antenna, of the type having a plurality of elements as in claim 1, said antenna comprising a length of waveguide having one thick wide wall, said wall having a plurality of cylindrical openings therein, said wide wall having a thickness greater than one-quarter wavelength and said cylindrical openings having a depth of one-quarter wavelength; an aperture in the center of each of said openings; a plurality of grooves in the upper center of said thick wall of said waveguide, each groove I connecting alternate pairs of adjacent cylindrical openings; and a U-shaped probe positioned in each of said grooves so that the ends of said probes project through said apertures.

4. Apparatus for radiating electromagnetic energy comprising, a section of rectangular waveguide one-quarter wavelength long and short circuited at one end thereof, said waveguide being dimensioned in cross section to operate only in the dominant mode, said section of waveguide having a small aperture positioned in the center of said short circuited end through which said section of waveguide is energized; and a feed probe extending centrally along the length of said section of waveguide, said feed probe having one end bent and fastened to the center of one of the broader walls at the open end of said section of waveguide, said feed probe having its other end projecting through said aperture in said short circuited end of said section of waveguide whereby said feed probe when energized excites an electromagnetic field in said section of waveguide.

5. An antenna array comprising a length of rectangular waveguide, a plurality of one-quarter wavelength waveguide sections extending from a broad wall of said waveguide, said broad wall closing one end of each of said waveguide sections, said broad wall being formed with a plurality of openings therein, each of said openings being disposed at the center of a closed end of one of said waveguide sections, each of said waveguide sections being provided with a feed probe extending centrally along the length of said waveguide section, said feed probe having one end bent and fastened to a wall at the open end of said waveguide section, said feed probe having its other end projecting through said opening in said closed end and into said waveguide whereby electromagnetic energy in said waveguide energizes said feed probe.

6. An antenna array as in claim 5 wherein said one quarter wavelength waveguide sections are rectangular in cross sectlon.

7. An antenna array comprising, a length of rectangular waveguide, a plurality of one-quarter wavelength rectangular waveguide sections extending from a broad wall of said waveguide, said waveguide sections having their broader wall perpendicular to the longitudinal axis of said waveguide, said broad wall of said waveguide closing one end of each of said waveguide sections, said broad wall of said waveguide being formed with a plurality of openings therein, each of said openings being disposed at the center of a closed end of one of said waveguide sections, each of said waveguide sections being provided with a feed probe extending centrally along the length of said waveguide section, said feed probes having one end bent and fastened to a broad wall of said waveguide section at the open end thereof, said feed probe having its other end projected through said openings in said closed end and into said waveguide whereby electromagnetic energy in said waveguide energizes said feed probe.

8. Apparatus as in claim 7 wherein said waveguide sections have a cross section substantially identical to the cross section of said waveguide.

9. Apparatus as in claim 7 wherein the spacing between the centers of said waveguide sections measured along the longitudinal axis of said waveguide is greater than the narrower dimension of said waveguide sections.

10. Apparatus as in claim 7 wherein the spacing between the centers of said waveguide sections measured along the longitudinal axis of said waveguide is greater than the narrower dimension of said waveguide sections, said antenna array further comprising, conductive members disposed between adjacent waveguide sections and electrically connected to the broad walls thereof at said open end of said waveguide sections.

11. An antenna array comprising, a length of a rectangular waveguide, a plurality of one-quarter wavelength waveguide sections extending from a broad wall of said waveguide, said broad wall closing one end of each of said waveguide sections, said broad wall being formed at a plurality of openings therein, each of said openings being disposed at the center of a closed end of one of said Waveguide sections, each of said waveguide sections being provided with a feed probe extending centrally along the length of said waveguide section, said feed probe having one end bent and fastened to a wall at the open end of said waveguide section, said feed probe having its other end projecting through said openings in said closed end and into said waveguide whereby electromagnetic energy in said waveguide energizes said feed probe, and a conductive member extending parallel to the said broad wall of said waveguide and spaced therefrom by substantially one-quarter wavelength, said conductive member being formed with openings therein coincident with the open ends of said waveguide sections.

References Cited in the file of this patent UNITED STATES PATENTS 2,349,942 Dallenbach May 30, 1944 2,402,622 Hansen June 25, 1946 2,414,266 Lindenblad Jan. 14, 1947 12,414,376 Heim Jan. 14, 1947 2,425,716 Barrow Aug. 19, 1947 2,427,693 Ryder Sept. 23, 1947 

